Flaxseed oil is derived from the hard, tiny seeds of the flax plant. It has been proposed as a less smelly alternative to fish oil. Like fish oil, flaxseed oil contains omega-3 fatty acids, a type of fat your body needs as much as it needs vitamins.

However, it's important to realize that the omega-3 fatty acids in flaxseed oil aren't identical to what you get from fish oil. Flaxseed oil contains alpha-linolenic acid (ALA), while fish oil contains eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The effects and potential benefits may not be the same.

Whole
flaxseeds contain another important group of chemicals known as
lignans.Lignans are being studied for use in preventing cancer. However, flaxseed
oilcontains no lignans.
1

The best use of flaxseed oil is as a general nutritional supplement to provide essential fatty acids. There is little evidence that it is effective for any specific therapeutic purpose.

Flaxseed oil has been proposed as a less smelly alternative to fish oil for the prevention of
heart disease . However, there is as yet no consistent evidence that it works. One double-blind study of 56 people failed to find that flax oil improved
cholesterol profile .
2 Other studies did find improvements in cholesterol and/or
blood pressure , but these were small trials and suffered from serious problems in study design.
3
One study found that a diet high in ALA (from sources other than flaxseed oil) was associated with a reduced risk of heart disease.
4 However, there were so many other...

Safety Issues

Flaxseed oil appears to be a safe nutritional supplement when used as recommended. However, due to the contradictory evidence regarding its effects on cancer (as described above), it should not be taken by people at high risk of cancer except on physician’s advice.